linux-kernel - Re: [RFC] perf report: introduce --map-anon-mem for anon-executable-memory symbols parsing

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Date:	Mon, 22 Jun 2015 12:53:49 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Hou Pengyang <houpengyang@...wei.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	"Wangnan (F)" <wangnan0@...wei.com>, mingo@...hat.com,
	namhyung@...nel.org, a.p.zijlstra@...llo.nl,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] perf report: introduce --map-anon-mem for
 anon-executable-memory symbols parsing

Em Mon, Jun 22, 2015 at 11:22:13PM +0800, Hou Pengyang escreveu:
> On 2015/6/19 18:42, Ingo Molnar wrote:
> >
> >* Wangnan (F) <wangnan0@...wei.com> wrote:
> >
> >>On 2015/6/18 22:01, Hou Pengyang wrote:
> >>>This patch introduces a --map-anon-mem argument to perf report to deal
> >>>with anon-executable-memory symbol parsing.
> >>
> >>--map-anon-mem is not a good name. The user defined map area list
> >>introduced in this patch can be used on not only anon mapping but
> >>also file mapping.
> >
> >Yeah, so quirky options generally suck and only 0.01% of the users will use it.
> >It's in a way worse than not having this code, because we'll have to maintain it,
> >but it won't be used.
> >
> >Is there a way to auto-detect 'executable anon mappings' (perhaps by generating an
> >MMAP event with some extra bit set, or a new MMAP event?) so that it's all
> >seemless?
> >
> I think it not difficult to generate such MMAP event, just like :
> 	
> 	0 435090424309600 0x3e0 [0x68]: PERF_RECORD_MMAP2
> 788/788:[0x7f946c0000(0x4000) @ 0x7f946c0000 00:00 0 0]: ---p //anon
> 
> But for symbol parsing, this is not enough. For such mmap area, perf
> doesn't know the path of '.so/.o', which is necessarcy for symbol-
> parsing. So we need to tell perf the relationship between the .so file and
> the mmap range explicitly.

What is done to provide maps for JIT is detailed at:

tools/perf/Documentation/jit-interface.txt

Are you sure that can't be used for you guys? Its already automagically
done, you just have to provide a file for that pid with the mappings.

Sure, it is not for ELF, but that could be easily done, just autodetect
the map type.

- Arnaldo

 
> Thanks,
>      Hou
> 
> >The user should not be required to know about such details!
> >
> >Thanks,
> >
> >	Ingo
> >--
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> >
> >
> 
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